Mizter T wrote:

(Indeed what's the cheapest way to get a good discount on an extension
from
a 1-6 travelcard to Aylesbury? PAYG to Amersham, then buy a return
ticket at
the office there and on the way back jump onto the platform to touch in
then
back onto the train, or a straightforward extension from
Marylebone/Harrow?)

If you're using Oyster PAYG (on either the Met or Chiltern) then you'd
need to touch out at Amersham, likewise coming back from Aylesbury
you'd need to touch in again (if you don't you're subject to a Penalty
Fare, the unresolved journey doesn't contribute to your daily cap and
from November you'll be charged £4 for unresolved journeys). At
Amersham there's gates in operation, at least some of the time, which
might well make jumping off and on the same train a bit of an
impossible mission!

There are also readers on the London bound platform (at least - I've never
looked on the other two). I have managed to jump off touch in jump on for a
single train before but I agree it's messy.

Not knowing how often you'll have to make the journey, at what time
you'll be setting off and where you're starting from it's hard to say
what you're best option is.

Generally I travel during the day - anytime leaving Baker Street any time
from noon til three. It's a journey probably made on average every three
months.

Remember that (in theory at least) you could buy a YPR-discounted Day
Travelcard from an LU ticket office (thus getting the free zones A-D)
in advance.

Yup - but aside from all the hassle, I have a zones 1-6 season travelcard so
I'm looking at the extension option only.